Study On Flame Retardance And Smoke Suppression Of Thermoplastic Polyurethane

Thermoplastic polyurethane (TPU) is one of the most versatile engineeringthermoplastics with elastomeric properties. Because of its high performance, includingexcellent abrasion resistance, high tensile strength, high compressive and tear strength,good flexibility, and good hydrolytic stability, TPU has been widely used in muchindustrial area, such as wires and cables, conveyor belts, and protective coatings.However, its flammability and molten dripping nature restrict its applications. It isimportant to improve the flame retardancy of TPU. Currently, due to the rise ofintumescent system, the majority applied in TPU are halogen-free intumescent flameretardants. However, due to the large amount of addition, there is a great impact onmechanical properties of TPU and a negative impact on its application. Furthermore,there is also a large amount of toxic smoke released from intumescent flame retardantTPU composites during combustion. Now, most of people turned to the study of theflame retardant TPU. So developing the retardants with synergistic effects of flameretardant and smoke suppression is the key to furtherly explore the TPU applications.This paper aims to study of flame retardant and smoke suppression properties ofTPU. We want to achieve the goal of the flame retardant and smoke suppression ofTPU, with these four kind of iron series compounds (FeOOH, Fe, Fe2O3andferrocene), hollow glass microsphere and fumed silica with good thermal insulation assmoke suppression agent or synergism based on ammonium polyphosphate (APP) asflame retardant. The smoke suppression and flame retardant properties of TPUcomposites were mainly evaluated by smoke density test (SDT), cone calorimeter test(CCT), thermogravimetric (TG) analysis, and limit oxygen index (LOI). The charresidues of TPU composites left after cone calorimeter test were examined by scanningelectron microscopy (SEM) analysis.The results show that the smoke suppression and flame retardant effect of iron series compounds such as FeOOH is obvious. The addition of3.75wt%FeOOH and16.25wt%APP makes the luminous flux value of TPU materials increased from18.7%to88.6%; The addition of2.5wt%Fe and17.5wt%APP makes the TSR valueof TPU materials decreased from1033.5m2/m2to553.4m2/m2; The addition of2.5wt%Fe2O3and17.5wt%APP makes the PHRR value of TPU materials was reducedby95.6%. The results of SEM show that the structure and density of the carbon layeris closely related to the heat release and smoke release of the materials. The iron seriessmoke suppression agents have a promoting effect on the formation of a dense carbonlayer, and improve the structure of carbon layer. The results of TG show that the ironseries smoke suppression agents have reduced the initial thermal decompositiontemperature of the composites. The protective char layers are formed in advance toprevent the further pyrolysis of materials.The smoke suppression and flame retardant effect of hollow microsphere andfumed silica is also apparent. When the content of hollow microsphere increases from0.625wt%to2.5wt%, the luminous flux values of TPU materials increase from38.7%to75.4%. The addition of fumed silica makes the luminous flux of TPU reachmore than90%.The results of SEM show that hollow microsphere and fumed silica allcan improve the structure of carbon layer. The results of TG show that hollowmicrosphere and fumed silica have reduced the initial thermal decompositiontemperature of the composites. The protective char layers are formed in advance.